Methods, devices and systems for parallel video encoding and decoding

ABSTRACT

A method for decoding a video bitstream is disclosed. The method comprises: entropy decoding a first portion of a video bitstream, wherein first portion of video bitstream is associated with a video frame, thereby producing a first portion of decoded data; entropy decoding a second portion of video bitstream, wherein second portion of video bitstream is associated with video frame, thereby producing a second portion of decoded data, wherein entropy decoding second portion of video bitstream is independent of entropy decoding first portion of video bitstream; and reconstructing a first portion of video frame associated with video bitstream using first portion of decoded data and second portion of decoded data.

This application is a continuation of application Ser. No. 16/375,474,filed Apr. 4, 2019, which is a continuation of application Ser. No.15/897,510, filed Feb. 15, 2018, now issued as U.S. Pat. No. 10,284,881,which is a continuation of application Ser. No. 15/493,093, filed Apr.20, 2017, now issued as U.S. Pat. No. 9,930,369, which is a continuationof application Ser. No. 15/254,421, filed Sep. 1, 2016, now issued asU.S. Pat. No. 9,681,143, which is a continuation of application Ser. No.15/040,482, filed Feb. 10, 2016, now issued as U.S. Pat. No. 9,503,745,which is a continuation of application Ser. No. 14/269,755, filed May 5,2014, now issued as U.S. Pat. No. 9,473,772, which is a division ofapplication Ser. No. 12/934,938, filed Sep. 27, 2010, now issued as U.S.Pat. No. 8,824,541. Application Ser. No. 12/934,938, filed Sep. 27,2010, is a national phase application under 35 U.S.C. 071 of PCTapplication no. PCT/JP2009/056778, filed on Mar. 25, 2009. PCTapplication no. PCT/JP2009/056778 is a continuation of patentapplication Ser. No. 12/058,301 filed on Mar. 28, 2008, now issued asU.S. Pat. No. 8,542,748. The entire contents of all the foregoingapplications are hereby incorporated by reference.

TECHNICAL FIELD

Embodiments of the present invention relate generally to video coding.

BACKGROUND ART

State-of-the-art video-coding methods and standards, for exampleH.264/MPEG-4 AVC (H.264/AVC), may provide higher coding efficiency thanolder methods and standards at the expense of higher complexity.Increasing quality requirements and resolution requirements on videocoding methods and standards may also increase their complexity.Decoders that support parallel decoding may improve decoding speeds andreduce memory requirements. Additionally, advances in multi-coreprocessors may make encoders and decoders that support parallel decodingdesirable.

H.264/MPEG-4 AVC [Joint Video Team of ITU-T VCEG and ISO/IEC MPEG,“H.264: Advanced video coding for generic audiovisual services,” ITU-TRec. H.264 and ISO/IEC 14496-10 (MPEG4—Part 10), November 2007], whichis hereby incorporated by reference herein in its entirety, is a videocodec specification that uses macroblock prediction followed by residualcoding to reduce temporal and spatial redundancy in a video sequence forcompression efficiency.

DISCLOSURE OF THE INVENTION

Some embodiments of the present invention comprise methods, devices andsystems for parallel entropy encoding and decoding of a video bitstreambased on partitioning of data into entropy slices that may be entropyencoded and decoded independently.

According to one aspect of the present application, a method fordecoding a video bitstream is provided. The method comprises: entropydecoding a first portion of a video bitstream, wherein first portion ofvideo bitstream is associated with a video frame, thereby producing afirst portion of decoded data; entropy decoding a second portion ofvideo bitstream, wherein second portion of video bitstream is associatedwith video frame, thereby producing a second portion of decoded data,wherein entropy decoding second portion of video bitstream isindependent of entropy decoding first portion of video bitstream; andreconstructing a first portion of video frame associated with videobitstream using first portion of decoded data and second portion ofdecoded data.

According to another aspect of the present application, a method fordecoding a video frame in a video sequence is provided. The methodcomprises receiving a bitstream; identifying a reconstruction slice inbitstream; identifying a plurality of entropy slices associated withreconstruction slice in bitstream; entropy decoding each of plurality ofentropy slices associated with reconstruction slice, thereby producing aplurality of entropy-decoded entropy slices; and reconstructing aportion of a video frame associated with reconstruction slice usingplurality of entropy-decoded entropy slices.

According to another aspect of the present application, a method forencoding a video frame in a video sequence is provided. The methodcomprises: partitioning a first frame in a video sequence into at leastone reconstruction slice, thereby producing a first reconstructionslice; and partitioning first reconstruction slice into a plurality ofentropy slices.

According to another aspect of the present application, a method forgenerating a video bitstream for parallel decoding is disclosed. Themethod comprises: receiving a first video bitstream; identifying areconstruction slice in video bitstream; entropy decoding a plurality ofsymbols from reconstruction slice, thereby producing entropy-decodeddata associated with reconstruction slice; partitioning entropy-decodeddata associated with reconstruction slice into a plurality of entropyslices associated with reconstruction slice; independently entropyencoding the entropy-decoded data of each entropy slice of plurality ofentropy slices, thereby producing a plurality of entropy-encoded entropyslices; and generating a second video bitstream comprising plurality ofentropy-encoded entropy slices.

In some embodiments of the present invention, a first portion and secondportion of an input compressed-video bitstream may be entropy decodedindependently. A block of samples of a video frame associated with thesecond portion of the input compressed-video bitstream may bereconstructed using decoded data from the first portion and the secondportion. Thus, the reconstruction neighbor definition and the entropydecoding neighbor definition are not the same.

In some embodiments of the present invention, an encoder may partitioninput data into entropy slices. The encoder may entropy encode theentropy slices independently. The encoder may form a bitstreamcomprising entropy-slice headers each of which may indicate the locationin the bitstream of the associated data for the entropy slice. In someembodiments of the present invention, a decoder may parse a receivedbitstream for entropy-slice headers, and the decoder may entropy decodea plurality of entropy slices according to a decoder-defined level ofparallelism.

In some embodiments of the present invention, data may be multiplexed ata picture level to form entropy slices. In some embodiments, one, ormore, entropy slices may correspond to prediction data, and one, ormore, entropy slices may correspond to residual data. In alternativeembodiments of the present invention, one, or more, entropy slices maycorrespond to each of a plurality of color planes.

In some embodiments of the present invention, a bitstream may betranscoded to comprise entropy slices. In these embodiments, a receivedbitstream may be entropy decoded, a plurality of entropy slices may beconstructed, and each of the entropy slices may be independent encodedand written to a transcoded bitstream with an associated entropy-sliceheader.

The foregoing and other objectives, features, and advantages of theinvention will be more readily understood upon consideration of thefollowing detailed description of the invention taken in conjunctionwith the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a picture showing an H.264/AVC video encoder (prior art);

FIG. 2 is a picture showing an H.264/AVC video decoder (prior art);

FIG. 3 is a picture showing an exemplary slice structure (prior art);

FIG. 4 is a picture showing an exemplary slice group structure (priorart);

FIG. 5 is a picture showing an exemplary slice partition according toembodiments of the present invention, wherein a picture may bepartitioned in at least one reconstruction slice and a reconstructionslice may be partitioned into more than one entropy slice;

FIG. 6 is chart showing an exemplary embodiment of the present inventioncomprising an entropy slice;

FIG. 7 is a chart showing an exemplary embodiment of the presentinvention comprising parallel entropy decoding of multiple entropyslices followed by slice reconstruction;

FIG. 8 is a chart showing an exemplary embodiment of the presentinvention comprising prediction data/residual data multiplexing at thepicture level for entropy slice construction;

FIG. 9 is a chart showing an exemplary embodiment of the presentinvention comprising color-plane multiplexing at the picture level forentropy slice construction; and

FIG. 10 is a chart showing an exemplary embodiment of the presentinvention comprising transcoding a bitstream by entropy decoding,forming entropy slices and entropy encoding.

REFERENCE NUMERALS

-   2 H.264/AVC VIDEO ENCODER-   32 ENTROPY ENCODING-   54 ENTROPY DECODING-   80 H.264/AVC VIDEO DECODER-   110 VIDEO FRAME-   111, 112, 113 RECONSTRUCTION SLICE-   112-1, 112-2, 112-3 ENTROPY SLICE-   115, 116, 117, 118, 119, 120, 121, 122, 123 MACROBLOCK

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments of the present invention will be best understood byreference to the drawings, wherein like parts are designated by likenumerals throughout. The figures listed above are expressly incorporatedas part of this detailed description.

It will be readily understood that the components of the presentinvention, as generally described and illustrated in the figures herein,could be arranged and designed in a wide variety of differentconfigurations. Thus, the following more detailed description of theembodiments of the methods, devices and systems of the present inventionis not intended to limit the scope of the invention but it is merelyrepresentative of the presently preferred embodiments of the invention.

Elements of embodiments of the present invention may be embodied inhardware, firmware and/or software. While exemplary embodiments revealedherein may only describe one of these forms, it is to be understood thatone skilled in the art would be able to effectuate these elements in anyof these forms while resting within the scope of the present invention.

While any video coder/decoder (codec) that uses entropyencoding/decoding may be accommodated by embodiments of the presentinvention, exemplary embodiments of the present invention will beillustrated in relation to an H.264/AVC encoder and an H.264/AVCdecoder. This is intended for illustration of embodiments of the presentinvention and not limitation.

State-of-the-art video-coding methods and standards, for exampleH.264/AVC, may provide higher coding efficiency than older methods andstandards at the expense of higher complexity. Increasing qualityrequirements and resolution requirements on video coding methods andstandards may also increase their complexity. Decoders that supportparallel decoding may improve decoding speeds and reduce memoryrequirements. Additionally, advances in multi-core processors may makeencoders and decoders that support parallel decoding desirable.

H.264/AVC, and many other video coding standards and methods, are basedon a block-based hybrid video-coding approach, wherein the source-codingalgorithm is a hybrid of inter-picture, also considered inter-frame,prediction, intra-picture, also considered intra-frame, prediction andtransform coding of a prediction residual. Inter-frame prediction mayexploit temporal redundancies, and intra-frame and transform coding ofthe prediction residual may exploit spatial redundancies.

FIG. 1 shows a block diagram of an exemplary H.264/AVC video encoder 2.An input picture 4, also considered an input frame, may be presented forencoding. A predicted signal 6 and a residual signal 8 may be produced,wherein the predicted signal 6 may be based on either an inter-frameprediction 10 or an intra-frame prediction 12. The inter-frameprediction 10 may be determined by motion compensating 14 using astored, reference picture 16, also considered reference frame, usingmotion information 19 determined by a motion estimation 18 processbetween the input frame (input picture) 4 and the reference frame(reference picture) 16. The intra-frame prediction 12 may be determinedby intra-frame prediction 20 using a decoded signal 22. The residualsignal 8 may be determined by subtracting the input frame 4 from theprediction (predicted signal) 6. The residual signal 8 is transformed,scaled and quantized 24, thereby producing quantized, transformcoefficients 26. The decoded signal 22 may be generated by adding thepredicted signal 6 to a signal 28 generated by inverse transforming,scaling and inverse quantizing 30 the quantized, transform coefficients26. The motion information 19 and the quantized, transform coefficients26 may be entropy coded 32 and written to the compressed-video bitstream34. An output image region 38, for example a portion of the referenceframe, may be generated at the encoder 2 by filtering 36 thereconstructed, pre-filtered signal (decoded signal) 22.

FIG. 2 shows a block diagram of an exemplary H.264/AVC video decoder 50.An input signal 52, also considered a bitstream, may be presented fordecoding. Received symbols may be entropy decoded 54, thereby producingmotion information 56 and quantized, scaled, transform coefficients 58.The motion information 56 may be combined by motion compensation 60 witha portion of a reference frame 84 which may reside in frame memory 64,and an inter-frame prediction 68 may be generated. The quantized,scaled, transform coefficients 58 may be inversely quantized, inverselyscaled and inversely transformed 62, thereby producing a decodedresidual signal 70. The residual signal 70 may be added to a predictionsignal 78: either the inter-frame prediction signal 68 or an intra-frameprediction signal 76, and become combined signal 72. The intra-frameprediction signal 76 may be predicted by intra-frame prediction 74 frompreviously decoded information (previously combined signal) 72 in thecurrent frame. The combined signal 72 may be filtered by de-blockingfilter 80 and the filtered signal 82 may be written to frame memory 64.

In H.264/AVC, an input picture is partitioned into fixed-sizemacroblocks, wherein each macroblock covers a rectangular picture areaof 16×16 samples of the luma component and 8×8 samples of each of thetwo chroma components. The decoding process of the H.264/AVC standard isspecified for processing units which are macroblocks. The entropydecoder 54 parses the syntax elements of the compressed-video bitstream52 and de-multiplexes them. H.264/AVC specifies two alternative methodsof entropy decoding: a low-complexity technique that is based on theusage of context-adaptively switched sets of variable length codes,referred to as CAVLC, and a computationally more demanding algorithm ofcontext-based adaptively binary arithmetic coding, referred to as CABAC.In both entropy decoding methods, decoding of a current symbol may relyon previously, correctly decoded symbols and adaptively updated contextmodels. In addition, different data information, for example, predictiondata information, residual data information and different color planes,may be multiplexed together. De-multiplexing may not be done untilelements are entropy decoded.

After entropy decoding, a macroblock may be reconstructed by obtaining:the residual signal through inverse quantization and the inversetransform, and the prediction signal, either the intra-frame predictionsignal or the inter-frame prediction signal. Blocking distortion may bereduced by applying a de-blocking filter to every decoded macroblock. Noprocessing may begin until the input signal is entropy decoded, therebymaking entropy decoding a potential bottleneck in decoding.

Similarly, in codecs in which alternative prediction mechanisms may beallowed, for example, inter-layer prediction in H.264/AVC or inter-layerprediction in other scalable codecs, entropy decoding may be requisiteprior to all processing at the decoder, thereby making entropy decodinga potential bottleneck.

In H.264/AVC, an input picture comprising a plurality of macroblocks maybe partitioned into one or several slices. The values of the samples inthe area of the picture that a slice represents may be correctly decodedwithout the use of data from other slices provided that the referencepictures used at the encoder and the decoder are identical. Therefore,entropy decoding and macroblock reconstruction for a slice do not dependon other slices. In particular, the entropy coding state is reset at thestart of each slice. The data in other slices are marked as unavailablewhen defining neighborhood availability for both entropy decoding andreconstruction. In H.264/AVC, slices may be entropy decoded andreconstructed in parallel. No intra prediction and motion-vectorprediction are allowed across the slice boundary. De-blocking filteringmay use information across slice boundaries.

FIG. 3 shows an exemplary video picture 90 comprising eleven macroblocksin the horizontal direction and nine macroblocks in the verticaldirection (nine exemplary macroblocks labeled 91-99). FIG. 3 shows threeexemplary slices: a first slice denoted “SLICE #0” 100, a second slicedenoted “SLICE #1” 101 and a third slice denoted “SLICE #2” 102. AnH.264/AVC decoder may decode and reconstruct the three slices 100, 101,102 in parallel. At the beginning of the decoding/reconstruction processfor each slice, context models are initialized or reset and macroblocksin other slices are marked as unavailable for both entropy decoding andmacroblock reconstruction. Thus, for a macroblock, for example, themacroblock labeled 93, in “SLICE #1,” macroblocks (for example,macroblocks labeled 91 and 92) in “SLICE #0” may not be used for contextmodel selection or reconstruction. Whereas, for a macroblock, forexample, the macroblock labeled 95, in “SLICE #1,” other macroblocks(for example, macroblocks labeled 93 and 94) in “SLICE #1” may be usedfor context model selection or reconstruction. Therefore, entropydecoding and macroblock reconstruction must proceed serially within aslice. Unless slices are defined using flexible macroblock ordering(FMO), macroblocks within a slice are processed in the order of a rasterscan.

Flexible macroblock ordering defines a slice group to modify how apicture is partitioned into slices. The macroblocks in a slice group aredefined by a macroblock-to-slice-group map, which is signaled by thecontent of the picture parameter set and additional information in theslice headers. The macroblock-to-slice-group map consists of aslice-group identification number for each macroblock in the picture.The slice-group identification number specifies to which slice group theassociated macroblock belongs. Each slice group may be partitioned intoone or more slices, wherein a slice is a sequence of macroblocks withinthe same slice group that is processed in the order of a raster scanwithin the set of macroblocks of a particular slice group. Entropydecoding and macroblock reconstruction must proceed serially within aslice.

FIG. 4 depicts an exemplary macroblock allocation into three slicegroups: a first slice group denoted “SLICE GROUP #0” 103, a second slicegroup denoted “SLICE GROUP #1” 104 and a third slice group denoted“SLICE GROUP #2” 105. These slice groups 103, 104, 105 may be associatedwith two foreground regions and a background region, respectively, inthe picture 90.

Some embodiments of the present invention may comprise partitioning apicture into one or more reconstruction slices, wherein a reconstructionslice may be self-contained in the respect that values of the samples inthe area of the picture that the reconstruction slice represents may becorrectly reconstructed without use of data from other reconstructionslices, provided that the references pictures used are identical at theencoder and the decoder. All reconstructed macroblocks within areconstruction slice may be available in the neighborhood definition forreconstruction.

Some embodiments of the present invention may comprise partitioning areconstruction slice into more than one entropy slice, wherein anentropy slice may be self-contained in the respect that symbol values inthe area of the picture that the entropy slice represents may becorrectly entropy decoded without the use of data from other entropyslices. In some embodiments of the present invention, the entropy codingstate may be reset at the decoding start of each entropy slice. In someembodiments of the present invention, the data in other entropy slicesmay be marked as unavailable when defining neighborhood availability forentropy decoding. In some embodiments of the present invention,macroblocks in other entropy slices may not be used in a current block'scontext model selection. In some embodiments of the present invention,the context models may be updated only within an entropy slice. In theseembodiments of the present invention, each entropy decoder associatedwith an entropy slice may maintain its own set of context models.

Some embodiments of the present invention may comprise CABACencoding/decoding. The CABAC encoding process includes the followingsteps:

Binarization: A non-binary-valued symbol (for example, a transformcoefficient, a motion vector, or other coding data) is converted into abinary code, also referred to as a bin string.

Binarization is followed, for each bin, also considered bit, of thebinarized symbol by:

Context Model Selection: A context model is a probability model for oneor more bins of the binarized symbol. The context model comprises, foreach bin, the probability of the bin being a “1” or a “0.” The model maybe chosen for a selection of available models depending on thestatistics of recently coded data symbols, usually based on the left andabove neighboring symbols, if available.

Binary Arithmetic Coding: An arithmetic coder encodes each bin accordingto the selected probability model and is based on recursive intervalsubdivision.

Probability Update: The selected context model is updated based on theactual coded value.

In some embodiments of the present invention comprising CABACencoding/decoding, at the decoding start of an entropy slice, all of thecontext models may be initialized or reset to predefined models.

Some embodiments of the present invention may be understood in relationto FIG. 5. FIG. 5 shows an exemplary video frame 110 comprising elevenmacroblocks in the horizontal direction and nine macroblocks in thevertical direction (nine exemplary macroblocks labeled 115-123). FIG. 5shows three exemplary reconstruction slices: a first reconstructionslice denoted “R_SLICE #0” 111, a second reconstruction slice denoted“R_SLICE #1” 112 and a third reconstruction slice denoted “R_SLICE #2”113. FIG. 5 further shows a partitioning of the second reconstructionslice “R_SLICE #1” 112 into three entropy slices: a first entropy slicedenoted “E_SLICE #0” shown in cross-hatch 112-1, a second entropy slicedenoted “E_SLICE #1” shown in vertical-hatch 112-2 and a third entropyslice denoted “E_SLICE #2” shown in angle-hatch 112-3. Each entropyslice 112-1, 112-2, 112-3 may be entropy decoded in parallel. Here,first entropy slice denoted “E_SLICE #0” and second entropy slicedenoted “E_SLICE #1” may also be referred to as first portion and secondportion of the bitstream.

In some embodiments of the present invention, only data from macroblockswithin an entropy slice may be available for context model selectionduring entropy decoding of the entropy slice. All other macroblocks maybe marked as unavailable. For this exemplary partitioning, macroblockslabeled 117 and 118 are unavailable for context model selection whendecoding symbols corresponding to the area of macroblock labeled 119because macroblocks labeled 117 and 118 are outside of the entropy slicecontaining macroblock 119. However, these macroblocks 117, 118 areavailable when macroblock 119 is reconstructed.

In some embodiments of the present invention, an encoder may determinewhether or not to partition a reconstruction slice into entropy slices,and the encoder may signal the decision in the bitstream. In someembodiments of the present invention, the signal may comprise anentropy-slice flag (entropy-slice flag in first entropy slice may bereferred to as first flag), which may be denoted “entropy_slice_flag” insome embodiments of the present invention.

Some decoder embodiments of the present invention may be described inrelation to FIG. 6. In these embodiments, an entropy-slice flag may beexamined (S130), and if the entropy-slice flag indicates that there areno entropy slices associated with a picture, or a reconstruction slice(NO in the step S130), then the header may be parsed as a regular sliceheader (S134). The entropy decoder state may be reset (S136), and theneighbor information for the entropy decoding and the reconstruction maybe defined (S138). The slice data may then be entropy decoded (S140),and the slice may be reconstructed (S142). If the entropy-slice flagindicates there are entropy slices associated with a picture (YES in thestep S130), then the header may be parsed as an entropy-slice header(S148). The entropy decoder state may be reset (S150), the neighborinformation for entropy decoding may be defined (S152) and theentropy-slice data may be entropy decoded (S154). The neighborinformation for reconstruction may then be defined (S156), and the slicemay be reconstructed (S142). After slice reconstruction in the stepS142, the next slice, or picture, may be examined.

Some alternative decoder embodiments of the present invention may bedescribed in relation to FIG. 7. In these embodiments, the decoder maybe capable of parallel decoding and may define its own degree ofparallelism, for example, consider a decoder comprising the capabilityof decoding N entropy slices in parallel. The decoder may identify Nentropy slices (S170). In some embodiments of the present invention, iffewer than N entropy slices are available in the current picture, orreconstruction slice, the decoder may decode entropy slices fromsubsequent pictures, or reconstruction slices, if they are available. Inalternative embodiments, the decoder may wait until the current picture,or reconstruction slice, is completely processed before decodingportions of a subsequent picture, or reconstruction slice. Afteridentifying up to N entropy slices in the step of S170, each of theidentified entropy slices may be independently entropy decoded. A firstentropy slice may be decoded (S172-S176). The decoding of the firstentropy slice may comprise resetting the decoder state (S172). In someembodiments comprising CABAC entropy decoding, the CABAC state may bereset. The neighbor information for the entropy decoding of the firstentropy slice may be defined (S174), and the first entropy slice datamay be decoded (S176). For each of the up to N entropy slices, thesesteps may be performed (S178-S182 for the Nth entropy slice). In someembodiments of the present invention, the decoder may reconstruct theentropy slices when all of the entropy slices are entropy decoded(S184). In alternative embodiments of the present invention, the decodermay begin reconstruction in the step of S184 after one or more entropyslices are decoded.

In some embodiments of the present invention, when there are more than Nentropy slices, a decode thread may begin entropy decoding a nextentropy slice upon the completion of entropy decoding of an entropyslice. Thus when a thread finishes entropy decoding a low complexityentropy slice, the thread may commence decoding additional entropyslices without waiting for other threads to finish their decoding.

In some embodiments of the present invention which may accommodate anexisting standard or method, an entropy slice may share most of theslice attributes of a regular slice according to the standard or method.Therefore, an entropy slice may require a small header. In someembodiments of the present invention, the entropy slice header may allowa decoder to identify the start of an entropy slice and start entropydecoding. In some embodiments, at the start of a picture, or areconstruction slice, the entropy slice header may be the regularheader, or a reconstruction slice header.

In some embodiments of the present invention comprising an H.264/AVCcodec, an entropy slice may be signaled by adding a new bit,“entropy_slice_flag” to the existing slice header. Table 1 lists thesyntax for an entropy slice header according to embodiments of thepresent invention, wherein C indicates Category and Descriptor u(1),ue(v) indicate some fixed length or variable length coding methods.

“first_mb_in_slice” specifies the address of the first macroblock in theentropy slice associated with the entropy-slice header. In someembodiments, the entropy slice may comprise a sequence of macroblocks.

“cabac_init_idc” specifies the index for determining the initializationtable used in the initialization process for the context mode.

TABLE 1 Syntax Table for Entropy Slice Header C Descriptor slice_header() {  entropy_slice_flag 2 u(1)  if (entropy_slice_flag) {first_mb_in_slice 2 ue(v) if (entropy_coding_mode_flag && slice_type !=I && slice_type != SI) cabac_init_idc 2 ue(v) }  }  else { a regularslice header ...  } }

In some embodiments of the present invention, entropy decoding a entropyslice may comprise initializing a plurality of context models; andupdating the plurality of context models during entropy decoding theentropy slice.

In some embodiments of the present invention, an entropy slice may beassigned a different network abstraction layer (NAL) unit type from theregular slices. In these embodiments, a decoder may distinguish betweenregular slices and entropy slices based on the NAL unit type. In theseembodiments, the bit field “entropy_slice_flag” is not required.

In some embodiments of the present invention, an entropy slice may beconstructed by altering the data multiplexing. In some embodiments ofthe present invention, the group of symbols contained in an entropyslice may be multiplexed the macroblock level. In alternativeembodiments of the present invention, the group of symbols contained inan entropy slice may be multiplexed at the picture level. In otheralternative embodiments of the present invention, the group of symbolscontained in an entropy slice may be multiplexed by data type. In yetalternative embodiments of the present invention, the group of symbolscontained in an entropy slice may be multiplexed in a combination of theabove.

Some embodiments of the present invention method comprises encoding avideo frame in a video sequence, which includes partitioning a frame ina video sequence into at least one reconstruction slice, therebyproducing a reconstruction slice; and partitioning the reconstructionslice into a plurality of entropy slices.

Some embodiments of the present invention comprising entropy sliceconstruction based on picture level multiplexing may be understood inrelation to FIG. 8 and FIG. 9. In some embodiments of the presentinvention shown in FIG. 8, prediction data 190 and residual data 192 maybe entropy encoded by prediction encoder 194, and residual encoder 196separately and multiplexed by picture-level multiplexer 198 at thepicture level. In some embodiments of the present invention, theprediction data for a picture 190 may be associated with a first entropyslice, and the residual data for a picture 192 may be associated with asecond entropy slice. The encoded prediction data and the encodedentropy data may be decoded in parallel. In some embodiments of thepresent invention, each partition comprising prediction data or residualdata may be partitioned into entropy slices which may be decoded inparallel.

In some embodiments of the present invention shown in FIG. 9, theresidual of each color plane, for example, the luma (Y) residual 200 andthe two chroma (U and V) residuals 202, 204, may be entropy encoded by Yencoder 206, U encoder 208, and V encoder 210 separately and multiplexedby picture-level multiplexer 212 at the picture level. In someembodiments of the present invention, the luma residual for a picture200 may be associated with a first entropy slice, the first chroma(U)residual for a picture 202 may be associated with a second entropyslice, and the second chroma residual(V) for a picture 204 may beassociated with a third entropy slice. The encoded residual data for thethree color planes may be decoded in parallel. In some embodiments ofthe present invention, each partition comprising color-plane residualdata may be partitioned into entropy slices which may be decoded inparallel. In some embodiments of the present invention, the lumaresidual 200 may have relatively more entropy slices compared to thechroma residuals 202, 204.

In some embodiments of the present invention, a compressed-videobitstream may be transcoded to comprise entropy slices, thereby allowingfor parallel entropy decoding as accommodated by embodiments of thepresent invention described above. Some embodiments of the presentinvention may be described in relation to FIG. 10. An input bitstreamwithout entropy slices may be processed picture-by-picture according toFIG. 10. In these embodiments of the present invention, a picture fromthe input bitstream may be entropy decoded (S220). The data which hadbeen coded, for example, mode data, motion information, residualinformation and other data, may be obtained. Entropy slices may beconstructed one at a time from the data (S222). An entropy-slice headercorresponding to an entropy slice may be inserted in a new bitstream(S224). The encoder state may be reset and the neighbor information maybe defined (S226). The entropy slice may be entropy encoded 228 andwritten to the new bitstream. If there is picture data that has not beenconsumed by the constructed entropy slices (NO in the step S230), thenanother entropy slice may be constructed in the step of S222, and theprocess of S224-S230 may continue until all of the picture data has beenconsumed by the constructed entropy slices (YES in the step S230), andthen the next picture may be processed.

The terms and expressions which have been employed in the foregoingspecification are used therein as terms of description and not oflimitation, and there is no intention in the use of such terms andexpressions of excluding equivalence of the features shown and describedor portions thereof, it being recognized that the scope of the inventionis defined and limited only by the claims which follow.

The invention claimed is:
 1. An apparatus comprising: a non-transitorycomputer-readable medium having stored thereon instructions that, whenexecuted by one or more processors, cause the one or more processors toperform operations to generate image data corresponding to a videobitstream, the image data comprising: a plurality of pictures in thevideo bitstream including a first picture comprising a plurality ofblocks of samples that are entropy encoded; and a plurality of headersincluding a first header associated with the first picture and a secondheader associated with the first picture, wherein the second header isdifferent than the first header and shares most of attributes with thefirst header, wherein a value of a one bit parameter for the firstheader indicates that the first header is a regular header, and whereina value of the one bit parameter for the second header indicates thatthe second header is not a regular header, wherein the value of the onebit parameter for the first header is set to 0 to indicate that thefirst header is a regular header.
 2. The apparatus of claim 1, wherein asize of the second header is smaller than a size of the first header.